Influence of managed bee pollination and attractants on yield and seed quality of safflower (Carthamus tinctorius L.)

Introduction

Safflower (Carthamus tinctorius L.) is an important rabi oilseed crop belonging to the family Asteraceae. It is believed to have originated in the Middle East and has been cultivated since ancient times for edible oil, medicinal purposes and natural dyes (Azeez et al., 2017) [3] . The crop is widely adapted to arid and semi-arid regions because of its drought tolerance and deep root system. In India, safflower is mainly cultivated in Maharashtra, Karnataka, Telangana andhra Pradesh and parts of Madhya Pradesh under rainfed conditions. Safflower occupies an important position among rabi oilseed crops because of its ability to produce stable yields under moisture stress conditions. The seeds are highly valued for their nutritional quality and contain about 28-38 per cent oil rich in polyunsaturated fatty acids, especially linoleic acid, which is beneficial to human health. Safflower oil is considered a premium quality edible oil due to its low saturated fat content and high oxidative stability. Apart from edible uses, safflower oil finds applications in pharmaceuticals, cosmetics, paints and industrial products. The petals of safflower flowers contain colouring pigments such as carthamin and are traditionally used as dyes and herbal medicines.

The crop residues and seed cake are also utilized as animal feed because of their protein content (Singh and Mishra, 2019) [30] . Pollination is one of the most important biological processes in flowering plants and plays a major role in improving agricultural productivity. More than 75 per cent of flowering plants and nearly one-third of global crop production depend upon insect pollination either directly or indirectly (Roubik, 1995) [27] . Insect pollination not only increases crop yield but also improves seed quality, seed viability, oil content and uniformity in maturity. Among various insect pollinators, honey bees are considered the most efficient and economically important pollinating agents because of their flower constancy, foraging efficiency and ability to visit a large number of flowers within a short period (Winston, 1987) [31] . Although safflower is generally considered a self-pollinated crop, its floral morphology favours considerable cross-pollination through insects. The capitulum consists of numerous hermaphrodite, tubular florets that open progressively from the periphery to the center. Anthesis generally occurs during morning hours and the stigma becomes receptive shortly after. During foraging, bees facilitate the transfer of pollen grains from one floret to another, thereby increasing fertilization and seed set (Free, 1993) [8] . Studies have indicated that bee pollination in safflower significantly improves the number of filled seeds, seed weight, oil content and overall crop productivity (Panda et al., 1988) [19] . Managed pollination using European honey bees (Apis mellifera L.) has emerged as a reliable method to improve agricultural productivity. However, the activity of bees is heavily dependent on the floral resource density and environmental factors. To enhance bee activity on crops, chemical bee attractants have been evaluated. Bee attractants are substances capable of increasing the number of bee visits to flowers by stimulating their foraging behavior. Sugar-based formulations, jaggery solutions and commercial formulations like PARI have been used in various crops to enhance pollination and improve yields (Roubik, 1995; Kishanrao, 2001) [27,11] .

While several studies have assessed insect visitor diversity on safflower, comprehensive investigations comparing managed bee pollination, open pollination, pollinator exclusion and foliar sprays of bee attractants on yield attributes and physiological seed parameters are limited. Understanding these effects is essential for designing sustainable crop production practices and maximizing safflower yields. Therefore, the present investigation was undertaken to study the influence of pollination on the yield and quality parameters of safflower under the agro-climatic conditions of Bapatla andhra Pradesh, India.

Materials and Methods

The field experiment was conducted during the rabi season of 2025-26 at the Agricultural College Farm, Bapatla andhra Pradesh, India. The experimental site is situated at an altitude of 8 m above MSL, 15.922° N latitude and 80.480° E longitude, receiving an average annual rainfall of 914 mm. The soil of the experimental field was sandy clay loam in texture and sowing was done under irrigated conditions. The safflower variety used for the study was "Lakshmi Priya" (ISF-764), which is widely adapted to dryland and irrigated rabi farming systems. The seed material was procured from the ICAR-Indian Institute of Oil Seeds Research (IIOR), Rajendranagar, Hyderabad. The experiment was laid out in a Randomized Block Design (RBD) with three replications. The individual plot size measured 5.4 m × 4.0 m and sowing was done manually at a row-to-row spacing of 45 cm and plant-to-plant spacing of 20 cm, utilizing a seed rate of 8 kg ha -1 . Standard agronomic practices, excluding chemical plant protection measures during the flowering period, were adopted to raise the crop. Half of the recommended nitrogen (30 kg ha -1 ) and the full dose of phosphorus (30 kg ha -1 ) and potassium (20 kg ha -1 ) were applied as basal doses during the final land preparation and the remaining half of nitrogen was topdressed in two equal splits at 30 and 55 days after sowing (DAS). The study evaluated seven distinct pollination treatments, detailed as follows:

Treatment

Treatment Description T1 -Open Pollination

Plots were kept open to natural insect pollinators throughout the crop growth period.

T2 -Nylon Net with Apis mellifera

Plots were enclosed with insect-proof nylon nets (2 mm mesh size) at the onset of flowering and a managed four-frame colony of Apis mellifera with a prolific queen and adequate worker population was introduced inside each enclosure. T3 -Pollinator Exclusion (Nylon Net)

Plots were covered with insect-proof nylon nets before flowering to exclude all insect pollinators throughout the flowering period. T4 -Sugar Solution (50%)

Plots were sprayed once with a 50% sugar solution at 25% flowering during the morning hours (08:00 h) to attract pollinators. T5 -Jaggery Solution (50%)

Plots were sprayed once with a 50% jaggery solution at 25% flowering during the morning hours (08:00 h) to attract pollinators. T6 -Bee Attractant (PARI)

Plots were sprayed once with the commercial bee attractant PARI (Yash Udyog, Ahmednagar, Maharashtra) at 4 mL L⁻¹ of water at 25% flowering.

T7 -Water Spray

Plots were sprayed once with distilled water at 25% flowering during the morning hours (08:00 h) to serve as the foliar spray control.

Observations on yield parameters were recorded from twenty-five randomly selected plants in each replication per treatment before and after harvest. The parameters studied were: number of capitula per plant, number of seeds per capitulum, average capitulum weight (g), number of filled and unfilled seeds per capitulum, seed set percentage and seed filling percentage.

Seed set percentage was calculated using the formula:

Seed setting (%) = (Number of filled seeds per capitulum / Total number of florets per capitulum) x 100

Seed filling percentage was determined by dissecting seeds from the twenty-five selected capitula. At harvest, seed yield per plant was measured in grams and total plot yield was converted and expressed as seed yield per hectare (kg ha -1 ). Seed quality parameters were evaluated post-harvest. The test weight was recorded by weighing 1000 clean seeds on a digital balance. For germination studies, fifty seeds per treatment were placed in Petri dishes (15 cm diameter) lined with moistened filter paper. These were maintained at 25 ± 1°C and 75% relative humidity. The germination percentage was recorded after seven days. Seedling vigour was evaluated by measuring the shoot and root lengths of twenty-five seedlings per treatment. The seedling vigour index was computed using the standard formula of Abdul-Baki and Anderson (1973):

Seedling Vigour Index = (Shoot length + Root length in cm) x Germination percentage

Oil content percentage was estimated using Soxhlet extraction apparatus; 30 g of dried, ground seeds per treatment were extracted with n-hexane for 16 hours and the oil content was calculated gravimetrically. The quantitative data obtained were subjected to analysis of variance (ANOVA) for Randomized Block Design as per the procedure outlined by Gomez and Gomez (1984). The critical difference (CD) values were calculated at a 5% level of significance (P=0.05). Significant treatment means were grouped and compared using Duncan's Multiple Range Test (DMRT).

Results and Discussion

The findings of the present investigation clearly demonstrate that different modes of pollination and foliar application of bee attractants significantly influence the quantitative yield and qualitative seed parameters of safflower. The mean performance of safflower under various treatments for yield and quality attributes is summarized in Tables 1 and2.

Influence of Pollination on Yield and Yield Attributes

The number of capitula per plant did not vary significantly among the treatments (Table 1), ranging from a minimum of 29.11 in pollinator exclusion plots (T 3 ) to a maximum of 34.15 in plots caged with an A. mellifera colony (T 2 ). Plots sprayed with 50% jaggery solution (T 5 ), open pollinated plots (T 1 ) and bee attractant sprayed plots (T 6 ) recorded 32.87, 32.35 and 31.95 capitula per plant, respectively, which were on par with each other. The nonsignificant difference indicates that the number of capitula is primarily governed by the genetic potential of the variety and crop management practices rather than pollinator visits. These findings are in complete agreement with Kishanrao (2001) [11] , who reported non-significant differences in capitula production in safflower across pollination systems, recording 27.43, 26.70 and 25.63 capitula plant -1 under open pollination, managed bee pollination and pollinator exclusion, respectively. Similarly, Dhurve (2008) [7] in niger reported that pollinating insects exert a greater influence on seed production parameters than on vegetative yield attributes like capitula per plant.

In contrast, the number of seeds per capitulum was significantly influenced by the pollination treatments. 1). The significant increase in seeds per capitulum in T 2 emphasizes the role of bee visitation in ensuring successful fertilization. Honey bees gather and distribute pollen effectively among the florets. The present results are in line with Kishanrao (2001) [11] , who reported the highest seeds per capitulum (33.50) in plots provided with managed A. mellifera colonies and the lowest (24.01) under pollinator exclusion in safflower. The results are also supported by Rahman et al. (2022) [25] in sesame and Ranjitha et al. (2023) [26] in coriander, who observed that honey bee pollination significantly increased seeds per capsule/umbel over other treatments.

Capitulum weight was significantly higher in plots pollinated by A. mellifera (2.96 g), followed by T 4 (2.77 g), T 6 (2.73 g) and T 5 (2.69 g), which were on par with open-pollinated plots (2.68 g). The minimum capitulum weight was recorded in pollinator exclusion plots (2.09 g), while water sprayed plots recorded 2.59 g. The statistical difference among treatments was significant, with a CD value of 0.25 g. The increased weight in T 2 and attractant sprayed plots is directly attributable to the higher number of seeds set and better seed development resulting from effective pollination. This is corroborated by Prashanth and Belavadi (2009) [23] in pigeon pea, who reported significantly higher pod and seed weights under open pollination compared to self-pollinated caged plants. Similar observations were reported by Raghavendra (2018) [24] in sunflower, indicating that managed bee pollination improves reproductive success and photosynthetic assimilate partitioning towards developing heads. 1). The high proportion of unfilled seeds in pollinator-excluded plots highlights the high level of self-incompatibility or the limitation of mechanical self-pollination in safflower. Bees, through their active foraging, facilitate the cross-transfer and deep deposition of pollen, maximizing the fertilizing capacity of the florets. The present findings are in agreement with Pandey and Aloka (2008) [20] , who reported that naturally pollinated safflower heads recorded higher filled seeds (47.08) and lower unfilled seeds (7.67) than bagged heads (19.46 filled and 35.30 unfilled). These results are further supported by Öz et al. (2009) [17] in sunflower and Chaudhary et al. (2016) [6] in niger.

The seed yield per plant and per hectare differed significantly among the treatments. The highest seed yield per plant (42.56 g) and per hectare (2456.04 kg ha -1 ) was recorded in plots pollinated by A. mellifera (T 2 ), which was significantly superior to all other treatments. Among the bee attractants, sugar solution spray (T [11] , who reported the highest safflower yield of 2729.70 kg ha -1 in plots provided with managed A. mellifera colonies and the lowest in plots without insects (1552.00 kg ha -1 ). Similar yield increases via bee pollination have been reported in other oilseed crops like mustard (Patidar et al., 2017) [21] and niger (Sattigi et al., 2004; Chaudhary et al., 2016) [29,6] .

Influence of Pollination on Seed Quality and Physiological Parameters

The thousand-seed weight (test weight) did not differ significantly among the treatments (Table 2), ranging from 45.86 g in pollinator-excluded plots to 48.11 g in plots caged with A. mellifera. Similarly, open pollination recorded 46.45 g, sugar spray recorded 47.12 g and jaggery spray recorded 46.95 g. While bee pollination numerically improved the test weight, the lack of statistical significance indicates that seed weight is largely a genetically determined varietal trait controlled by maternal plant capacity rather than pollination intensity. However, the numerical superiority in bee-pollinated plots suggests that efficient fertilization ensures better endosperm development and seed filling. These results align with Kishanrao (2001) [11] , who observed that thousand-seed weight of safflower was numerically higher under bee pollination but largely conserved. Similar conclusions were drawn by Paiva et al. (2003) [18] in sunflower, where 100-seed weights were found to be statistically comparable among pollination systems.

Seed setting percentage and seed filling percentage showed significant differences among treatments. The highest seed setting (84.14%) and seed filling (94.18%) percentages were recorded in plots caged with A. mellifera (T 2 ), followed by sugar solution sprayed plots (81.32% and 89.04%), bee attractant PARI sprayed plots (80.66% and 88.39%) and jaggery solution sprayed plots (79.53% and 87.16%). Open pollination (T 1 ) recorded 77.91% seed setting and 86.70% seed filling, while the lowest values were observed under pollinator exclusion (65.90% and 74.60%). The CD values were 7.16% and 6.24% for seed setting and seed filling, respectively. The high seed setting and filling in T 2 are due to the abundance and frequency of bee visits, ensuring that almost all receptive stigmas received sufficient viable pollen grains. In contrast, self-pollination under caged conditions was inadequate, resulting in a large proportion of empty or partially filled seeds. The present findings confirm the results of Pandey and Aloka (2008) [20] in safflower, who reported 85.99 per cent seed set in open-pollinated capitula and only 35.54 per cent in bagged capitula. These results are also supported by Chaudhary et al.

(2016) [6] in niger and Patil and Pastagia (2016) [22] in sesame. Seed germination percentage did not vary significantly among the treatments (Table 2), ranging from 85.50% in pollinator exclusion plots (T 3 ) to 93.40% in A. mellifera pollinated plots (T 2 ). Other treatments such as sugar spray (T 4 ) and open pollination (T 1 ) recorded 90.56% and 89.23% germination, respectively.

Although bee pollination numerically improved germination, the non-significant variation suggests that seed viability is maintained at a high level across treatments, provided the seeds develop to maturity. These findings are in complete agreement with Paiva et al. (2003) [18] in sunflower, who concluded that pollination systems have a greater impact on overall seed production than on the germination capacity of the seeds. Similar observations were made by Nagpal et al. (2017) [16] in Indian mustard.

Seedling vigour and seedling vigour index, however, showed highly significant differences among treatments. The highest seedling vigour (11.26) [2] in sesame, who reported significantly higher seedling vigour in managed bee pollination plots compared to pollinator-excluded plots. Similar findings were reported by Nagpal (2016) [15] in mustard and Rao et al.

(2022) in sesame. Oil content percentage did not differ significantly among the treatments (Table 2), ranging from 22.07% in T 3 to 26.65% in T 2 .

Open-pollinated plots recorded 24.87% oil, while sugar solution and jaggery solution sprayed plots recorded 24.67% and 23.76% oil, respectively. Although numerically superior in bee-pollinated plots, the differences did not reach statistical significance (CD = 2.98%), indicating that seed oil percentage is primarily a genetic characteristic of the variety. Nonetheless, managed bee pollination significantly enhances total oil yield per unit area by increasing seed yields. The present results are in line with Kishanrao (2001) [11] in safflower and Raghavendra (2018) [24] in sunflower, who reported that oil content was non-significantly influenced by pollination systems, concluding that honey bee pollination primarily maximizes total seed productivity.

Conclusion

The present investigation underscores the critical role of honey bees and managed pollination systems in enhancing the yield and seed quality of safflower. Introducing managed Apis mellifera colonies into safflower fields significantly improved key yield attributes, such as seeds per capitulum, capitulum weight and filled seeds, leading to a 13.53 per cent increase in seed yield per hectare over open pollination and a 23.08 per cent increase over pollinator exclusion. Additionally, bee-mediated pollination improved physiological seed quality, producing seedlings with significantly higher vigour and vigour indices. Foliar application of bee attractants, particularly a 50% sugar solution sprayed at 25 per cent flowering, also proved highly effective in boosting yields. Although parameters such as capitula per plant, test weight, seed germination and oil percentage were found to be primarily controlled by genetics, managed pollination numerically enhanced them. Therefore, integrating managed honey bee hives (A. mellifera) and utilizing sugar solution sprays are highly recommended for safflower growers to maximize crop productivity, ensure seed quality and enhance economic returns in dryland and irrigated farming systems.

Acknowledgement

AcknowledgementsThe authors are highly grateful to the Department of Entomology, Agricultural College, Bapatla, Acharya N. G. Ranga Agricultural University (ANGRAU), for providing the necessary facilities and support to conduct this research. We also thank the ICAR-Indian Institute of Oil Seeds Research (IIOR), Rajendranagar, Hyderabad, for supplying the pure seed material of safflower variety Lakshmi Priya (ISF-764) used in this study.

References

1. Abdul-Baki AA, Anderson JD. Vigor determination in soybean seed by multiple criteria. Crop Sci. 1973;13(6):630633.
2. Alekya G, Koteswara Rao SR, Madhumathi T, Ramesh D. Influence of bee pollination on seed yield of sesame, Sesamum indicum Linnaeus. Indian J Entomol. 2025;107112.
3. Azeez MA, Nandini C, Rao MS. Oilseed crops and their pollination importance. J Oilseeds Res. 2017;34(2):85-92.
4. Boch R. Honey bee activity on safflower (Carthamus tinctorius L.). Can J Plant Sci. 1961;41:555-562.
5. Cecen S, Gurel F, Karaca A. Impact of honeybee and bumblebee pollination on alfalfa seed yield. Acta Agric Scand B Soil Plant Sci. 2008;58(1):77-81.
6. Chaudhary NK, Sadanand R, Singh RN. Effect of different mode of pollination on quantitative and qualitative traits of niger (Guizotia abyssinica Cass). Bioscan. 2016;11:119-120.
7. Dhurve SS. Impact of honey bee pollination on seed production of niger. Dharwad (Karnataka): University of Agricultural Sciences; 2008.
8. Free JB. Insect pollination of crops. 2nd ed. London: Academic Press; 1993. p. 320-340.
9. Gomez KA, Gomez AA. Statistical procedures for agricultural research. New York: John Wiley and Sons; 1984. p. 318-319.
10. Gregory AL, Robert GD. Honeybee-mediated cross-versus of 'Sharpblue' blueberry increases hastens ripening. J Am Soc Hortic Sci. 1991;116(5):770-773.
11. Kishanrao YA. Foraging behaviour of honey bees and its effect on seed yield of safflower (Carthamus tinctorius L.). Parbhani (Maharashtra): Marathwada Agricultural University; 2001.
12. Kumar N, Singh R. Role of honey bees in oilseed crop pollination. Indian J Entomol. 2018;80(4):1152-1158.
13. Mahmoud FM. Insects associated with sesame (Sesamum indicum L.) and the impact of insect pollinators on crop production. Pestic Phytomed. 2012;27(2):117-129.
14. Mazeed AR, Attia MA, Mohamed GG, Amer SM. Pollinator activity on the flowers of safflower Carthamus tinctorius and its effect on some qualitative and quantitative parameters of the plant in Sohag Governorate, Egypt. Egypt J Plant Prot Res Inst. 2024;7(3):276-287.
15. Nagpal K. Role of Apis spp. pollination in quality seed production of Indian mustard [MSc thesis]. Hisar (Haryana): Chaudhary Charan Singh Haryana Agricultural University; 2016. p. 74.
16. Nagpal KN, Yadav SY, Kumar YK, Singh RS. Effect of pollination modes on yield components in Indian mustard (Brassica juncea L.). 2017:187-194.
17. Öz M, Karasu A, Cakmak I, Goksoy AT, Turan ZM. Effects of honeybee (Apis mellifera) pollination on seed set in hybrid sunflower (Helianthus annuus L.). Afr J Biotechnol. 2009;8(6):1037-1043.
18. Paiva GJ, Terada Y, Toledo VA. Seed production and germination of sunflower (Helianthus annuus L.) in three pollination systems. Acta Sci Anim Sci. 2003;25(2):223-227.
19. Panda P, Sontakke BK, Mishra RC. Pollination requirements of safflower and role of honey bees in yield improvement. Indian Bee J. 1988;50(3):63-65.
20. Pandey AK, Kumari A. Pollination ecology of safflower (Carthamus tinctorius Linn). In: 7th International Safflower Conference; Wagga Wagga, Australia; 2008.
21. Patidar BK, Ojha KN, Khan IU. Role of honeybee (Apis mellifera) in enhancing yield of mustard in humid region of Rajasthan, India. Int J Curr Microbiol Appl Sci. 2017;6(7):1879-1882.
22. Patil PN, Pastagia JJ. Effect of bee pollination on yield of coriander, Coriandrum sativum Linnaeus. Int J Plant Prot. 2016;9(1):79-83.
23. Prashanth K, Belavadi VV. Role of flower visitors in pollination and pod set of pigeon pea, Cajanus cajan L. Bangalore (Karnataka): University of Agricultural Sciences; 2009.
24. Bangalore (Karnataka): University of Agricultural Sciences; 2018.
25. Rahman MZ, Reza ME, Hossain MS, Ali MR, Hossain MS. Effect of bee pollination on yield of sesame. Ecology Journal. 2022;4(1):1-7.
26. Ranjitha MR, Koteswara Rao SR, Rajesh A. Efficiency of European honey bees (Apis mellifera L.) over bee attractants in pollination and seed yield of coriander, Coriandrum sativum L. Indian J Entomol. 2023;85:11-16.
27. Roubik DW. Pollination of cultivated plants in the tropics. Rome: Food and Agriculture Organization; 1995. p. 45-67.
28. Rubis DD, Levin MD, McGregor SE. Effects of honey bee activity and cages on attributing of thin hull and normal safflower lines. Crop Sci. 1966;6:11-14.
29. Sattigi HN, Gundannavar KP, Kambrekar DN, Kulkarni KA. Effect of bee pollination on the yield parameters of niger quality, Karnataka. J Agric Sci. 2004;17:831-832.
30. Singh AK, Mishra OP. Pollinator diversity and abundance in oilseed ecosystems. J Entomol Res. 2019;43(1):25-31.
31. Winston ML. The biology of the honey bee. Cambridge (MA): Harvard University Press; 1987. p. 180-215.